DETAILS V 1.0:
The BuckyBot is essentially a robot to build big things … like houses, stadiums, city covers, orbital space stations, asteroid enclosures, Dyson spheres … that sort of thing. It consists of a mobile spider-like robot, like a hexapod, onto which we have installed a 3D printer's extruder head.
We are currently working with two configuration concepts. Both of these consist of a means of moving the beastie around and a means of orienting the print head in a manner that allows easy addition to what's already been built.
I need to define some terminology here.... “What's already been built” is a ponderous term I'd like to shorten to Antecedent – with a capital “A”. So, from here on, the Antecedent is the part of our structure that has already been built, and which the BuckyBot is crawling over and building upon.
The “spyder” is used for locomotion, orientation, and support of the articulated platform, or “head”. The head is designed to exhibit six Degrees-of-Freedom (6-DOF). The spyder only has three or four DOF. As BuckyBot matures we will strive to throw away as many of these degrees-of-freedom as we can. That simplifies the Bot mechanically as well as reduces kinematic complexity (linear algebra with much smaller matrices as you throw away degrees of freedom) of the control software.
Well, both of our designs have about the same spyder. One concept places the extrusion head underneath the spyder, the other places the extrusion head to the side of the spyder. The first design requires the BuckyBot to straddle its workpiece as it builds, the second requires the BuckyBot to climb the sides of the Antecedent (see? … much more concise...) as it builds.
We considered wheels for its mobility, but, they'd have to be articulated to grip as well as roll, so we decided to use hexapod, insect/spider-type legs to simplify the design. The things we build won't be smooth, solid sheets – rather, they'll be like Sierpinski tetrahedrons, which are full of holes. If we can build domes using a bug, then we'll re-visit
It has the ability to extrude plastic (in later generations we envision using metals, like welded stainless steel) like most 3D printers. What is unique is that BuckyBot has the ability to climb atop what it has already built, and add another layer to it. 3D printers fabricate one thin layer of an object at a time. Once a layer is finished, the printer moves the object to a position suitable for the extrusion of the next layer comprising the object. BuckyBot extrudes some chunk of the object using some stored pattern, the moves on to add more chunks along one edge of the previous chunk. Think of each “chunk” as being one “brick” in a brick wall. As the brick wall gets larger, the bricklayer simply climbs up on the wall to add length and/or height to the wall.
If there is no previous structure for the Bot to orient itself (the first course of “bricks”) the robot follows an alternate set of guidance or positioning rules (boundary conditions). For instance, it might follow a line on the floor, or a string staked and stretched, or travel from waypoint to waypoint under wireless guidance of a GPS-enabled device.
It doesn't make a solid “brick”. Our first Bot will make hollow octahedrons – re-orienting itself slightly as it moves. Octahedrons can be attached to each other in many ways to make a strong, rigid structures. We plan for BuckyBot to build walls consisting of octahedrons attached face-to-face. The first course (we call it the “Prime” course) of a structure will consist of the top half of octahedrons (pyramids...).
OK … there are profound implications of joining octahedra and/or tetrahedra together to make things. Lots of people have done it before, and one can find them all over the internet. However, because of the perceived complexity of building platonic solids, such structures are at best modest, and relegated to the curiosity bin (AKA “art”). I leave it to the reader to investigate the mico- and macroscopic pertinence and philosophy of platonic solids in the universe. They might just BE the universe. All we at BuckyBot want to do is just build a friggin' dome.
BuckyBot requires a reference. In a gravity well the direction “Down” serves as that reference. It is measured in two places by three-axis accelerometers attached to the spyder and the head. We don't need gyros – accelerometers should be sufficient. The instantaneous position of spyder and head must conform to simple geometrical rules stored in memory or updated wirelessly. It moves itself to re-orient itself to satisfy those rules.